DE3432353A1 - METHOD FOR PRODUCING HIGH MOLECULAR ACRYLAMIDE POLYMERISATS - Google Patents

Description

The invention relates to an improved process for the production of high molecular weight, water-soluble polymers and copolymers of acrylamide monomers by inverse emulsion, suspension or solution polymerization Use of extremely small amounts of erythorbic acid (isoascorbic acid) or its alkali metal salts.

Monomeric acrylamide is commercially available as a crystalline solid or as a 50 percent, inhibited, aqueous solution containing 25 ppm CuSO ₁ to prevent polymerization. The solid monomeric acrylamide also contains trace amounts of various metal ions as impurities which inhibit the polymerization process and therefore reduce the rate of polymerization and therefore require an increase in the reaction cycle times.

This inhibition problem is well known in the art. Various have been called chelating agents Compounds used to eliminate the interference from copper (II) or iron (III) ions and increase the effectiveness of the polymerization system for the monomeric acrylamide to improve. Examples of chelating agents are compounds such as Aminocarboxylic acids, i.e. ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (Versenex 80), and hydroxycarboxylic acids, e.g. tartaric acid and citric acid. There is one disadvantage associated with these chelating agents in the fact that they counteract the inhibition caused by contamination with metal ions, but they do themselves tend to have a delaying effect. Furthermore, these compounds are not in the low concentrations effective in which according to the invention erythorbic acid and its Salts are used. Finally, the uses of the aforementioned chelating agents are because of their significant toxicity is limited. They cannot be used in food products.

No prior art has been ascertained which describes or suggests the present invention.

The object of the invention is to provide chelating agents, which do not suffer from the difficulties of conventional agents and those without limitation as antioxidants can be used for food purposes.

The invention relates to a process for the production of a polymer by inverse emulsion polymerization of acrylamide in the presence of about 50 to about 250 ppm erythorbic acid and / or its alkali metal salts.

In the process according to the invention, compounds such as Erythorbic acid (isoascorbic acid), its alkali metal salts and riboflavin (vitamin B "), or mixtures thereof, as novel Additives used to increase the rate of polymerization. Polyacrylamides are used in cosmetics and foods Used as a thickener, binder, emulsifier and clarifier for fruit juices. All at the Additives used in practicing the invention are known compounds found in a food grade suitable quality are available and currently used in the food and beverage industry as Antioxidants and the like can be used.

Using the antioxidants according to the invention Acrylamide polymers of various molecular weights can be inversed according to any desired inverse which is suitable for commercial purposes Emulsion, suspension or solution polymerization processes are produced. Depending on the desired molecular weight high or low temperatures can be used, the choice being made depending on the respective process will. According to the invention, the rate of polymerization can be without loss of molecular weight

Increase the weight of the polymers, thereby increasing productivity is increased.

In the present invention, the predictability / reproducibility of the polymerization rate and the molecular weight becomes of the polymer is improved if solid crystalline acrylamide and / or the commercially available 50 percent aqueous inhibited monomer solution can be used.

Acrylamide is free-radically polymerized under an inert atmosphere of Np or COp gas at a pH of 3 to 8, using either inverse emulsion polymerization processes (Microsuspension) or solution polymerization processes can be used. cause pH values greater than 9 hydrolysis, while pH values below 2.5 cause crosslinking through imidization. The additives according to the invention with a rate-increasing effect can be used in both polymerization systems, as they are consistently water-soluble are. In the case of an inverse emulsion polymerization, a water-in-oil emulsion is present, whereas the microscopic Water droplets and the monomer in a continuous Oil phase, generally odorless mineral spirits (OMS = odorless mineral spirits) or kerosene.

The surfactant used in the inverse emulsion polymerization system (or a mixture of surfaces Agents) must be oil soluble with a hydrophile-lipophile balance (HLB) in the range of 1 to 12 and preferably from 4 to 6. There are different types of water-in-oil emulsifiers commercially available including sorbitan fatty acid esters, mono- and diglycerides of fatty acids, substituted Lanolins, polyoxyalkylene fatty acid esters, polyoxyethylene sorbitol esters, Polyoxyethylene sorbitan fatty acid esters, various Oleic and fatty acid alkanolamides, cholesterol and mixtures of related sterols and polyoxyethylene alcohols. The amount

the surfactant used can be from 0.5 to 20.0 g per 100 g of the oil phase and preferably from 2.0 vary up to 15.0 g per 100 g of the oil phase. The ratio of water to oil phase is preferably about 1: 2, can but generally 1: 5 to even 2: 1. For procedural reasons, it is best to use a minimum Amount of oil phase to use.

The polymerization temperature for the inverse emulsion system is generally in the range from about 20 to 80.degree. C., and preferably from 25 to 60.degree. The temperature range for the solution polymerization is generally 20 to 98 ⁰ C and distortion as 35 to 90 ⁰ C.

The monomer concentration for the solution polymerization system is generally 1 to 40 parts by weight of monomer per 100 parts by weight of water and preferably 5 to 20 parts by weight of monomer per 100 parts by weight of water. In the solution polymerization process no surfactant is used. The monomer concentration for the inverse emulsion polymerization system is generally from 30 to 60 parts by weight of monomer per 100 parts by weight of water, and is preferably 45 to 50 parts by weight of monomer per 100 parts by weight of water.

The additives according to the invention can be used in the free radical Polymerization of Monomers! Acrylamide and / or methacrylamide alone or in combination with other suitable ones Comonomers can be used. A number of different methods for generating free radicals are known, e.g. using water-soluble alkali metal salts such as ammonium, sodium or potassium peroxydisulphate. In the practical implementation of the process according to the invention make organic peroxides and free radical azo initiators or mixtures thereof a preferred class of initiators represent.

557.075-7-3A32353

The initiators used according to the invention can therefore be organic peroxides, free-radical azo initiators or any suitable mixtures of these compounds. The general initiator concentration for the inverse emulsion polymerization process is about 0.005 parts by weight per 100 parts by weight of monomer to 5.0 parts by weight per 100 parts by weight of monomer. Preferably it is about 0.05 parts by weight per 100 parts by weight of monomer to ₃₅ O parts by weight per 100 parts by weight of monomer. In particular, it is about 0.1 part by weight per 100 parts by weight of monomer to 2.5 parts by weight per 100 parts by weight of monomer. For solution polymerization, the general initiator concentration is about 0.1 part by weight per 100 parts by weight of monomer to 30 parts by weight per 100 parts by weight of monomer. Preferably it is from 0.5 to 100 parts by weight per 100 parts by weight of monomer to 20 parts by weight per 100 parts by weight of monomer. In particular, it is 1.0 part by weight per 100 parts by weight of monomer to part by weight per 100 parts by weight of monomer.

Examples of suitable initiators are listed below: tert-butyl peroctoate, tert-amyl peroctoate, tert-butyl peroxypivalate, tert-amyl peroxypivalate, Ä-cumyl peroxypivalate, tert-butyl peroxyneohexanoate, tert-amyl peroxyneohexanoate, tert-butyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, Dibenzoyl peroxide, diacetyl peroxide, dilauroyl peroxide, di- (2-ethylhexyl) peroxydicarbonate, di- (phenoxyethyl) peroxydicarbonate, 1,1-di- (tert-butylperoxy) -cyclohexane, 1,1-di- (tert-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di- (2-ethylhexanoylperoxy) -hexane, 2,5-dimethyl-2,5-di- (benzoylperoxy) -hexane, Di-tert-butyl peroxide, Di- (tert-butyldiperoxy) azelate, tert-butylcumyl peroxide, Azo-bis-isobutyronitrile, 2,2'-azo-bis- (2,4-dimethylvaleronitrile) , 2-tert-butylazo-2-cyano-4-methoxy-4-methylpentane, 2-tert-butylazo-2-cyano-4-methyIpentane, 2-tert-butylazo-2-cyanopropane, 2-tert-butylazo-2-cyanobutane, 1-tert-butyl-

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azo-i-cyanocyclohexane, tert-butyl hydroperoxide and cumene hydroperoxide .

Preferred additives that increase the rate of polymerization erythorbic acid and its alkali metal salts provide without loss of molecular weight of the polymer -

Although riboflavin (vitamin B ") a faster polymerization when erythorbic acid and its alkali metal salts result, the molecular weight of the polymer is significantly reduced. According to the invention, the preferred polymerization system is inverse emulsion polymerization is used, but solution and suspension polymerization systems are also used suitable for carrying out the invention.

The additive concentration used in an inverse emulsion polymerization to increase the rate of polymerization without affecting molecular weight, is generally 50 parts by weight per million parts by weight Monomer to 2000 parts by weight per million parts by weight of monomer. Preferably it is about 50 parts by weight per 1 million parts by weight of monomer to 500 parts by weight per 1 million parts by weight of monomer. In particular it is about 100 parts by weight per million parts by weight of monomer to 300 parts by weight per million parts by weight Monomer.

These additive concentrations can also be used in the solution or suspension polymerization process to increase the rate of polymerization can be used without adversely affecting the molecular weight of the polymer.

According to the invention, acrylamide is used as the monomer. This can, however, in combination with isopropyl acrylamide, acrolein, acrylic acid, acrylonitrile, butadiene, eutyl methacrylate,

Diallyl cyanamide, glycidyl acrylate, maleic anhydride, methacrylamide, Methacrylic acid, methyl acrylate, styrene, unsaturated acyl gelatins, unsaturated alkyds, vinyl acetate, Vinyl chloride, vinyl ethers, vinyl ketones, vinyl pyridines, N-vinyl pyrrolidone, sodium acrylate, ß-methacryloxyethyltrimethylammonium methyl sulfate (MTMMS) and N, N-dimethylaminoethyl methacrylate are polymerized. For some of the aforementioned monomers, the amount of comonomer affects the acrylamide used, the water solubility of the copolymer. It is also possible to use anionic, cationic or to produce amphoteric polymers depending on the choice of comonomer used together with acrylamide.

The invention is illustrated below with the aid of examples.

Definiti on en he d in Examples v erwend eten materials

Vitamin B ": Riboflavin from Roche

Vitamin C: Ascorbic Acid from Pfizer Inc.

Niacin: Nicotinic acid from Lonza

^ 64: Azo-bis-isobutyronitrile from Dupont

52: 2,2'-azo-bis (2,4-dimethylvaleronitrile) from Dupont "Solid" monomeric acrylamide from 2 sources:

1) Aldrich Chemical Company "99+% Electrophoresis Grade Gold label "

2) Fisher, reagent use monomer

3) 50 percent aqueous solution of monomeric acrylamide, inhibited with about 25 ppm copper (Cu ⁺⁴ *) from Dow Chemicals

OMS: Odorless mineral spirits, Shell Sol-71 from Shell Oil Co; Span ^ 80: sorbitan monooleate from ICI America, Inc.

EA: Erythorbic acid from Pfizer Inc.

NaEA: Sodium Erythorbate from Pfizer Inc.

Versenex ^ eO: diethylenetriaminepentaacetic acid, a chelate

The agent from Dow Chemicals Triple Distilled Water from Queen City Pure Water

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(Buffalo, N.Y.). Before use, this water was heated to boiling and allowed to cool below Np. To for use it was stored under an Np atmosphere. LUAZO ^ 55: 2-tert-butylazo-2-cyano-4-methoxy-4-methylpentane

by Lucidol Div., Pennwalt Corp. LUAZd-'7O: 2-tert-butylazo-2-cyano-4-methylpentane from

Lucidol Div., Pennwalt Corp. LUPERSOL ^ 223: Di- (2-ethylhexyl) peroxydicarbonate of

Lucidol Div., Pennwalt Corp. LUPERSOL® 256: 2,5-dimethyl-2,5-di- (2-ethylhexanoylperoxy) -hexane

by Lucidol Div., Pennwalt Corp.

Standard procedure

The following is the approach for a typical inverse emulsion polymerization using inhibited, 50 percent aqueous acrylamide stated:

100 g aqueous acrylamide solution, inhibited with ~ ^ 25 ppm CuSOj. ("^ 50 weight percent aqueous acrylamide) 200 g OMS
20 g Span®80

0.10 g initiator (based on the pure substance) per 100 g monomer (based on the pure substance) 50 to 500 ppm additive based on the weight of the monomer, preferably 100 to 300 ppm.

The aqueous acrylamide was weighed to +0.05 g using a torsion balance and then set aside. OMS and

(R ")
Span ^K ^ 80 were weighed to +0.1 g together with a three-beam balance and then stirred for a few minutes to form a homogeneous solution.

The aqueous acrylamide and the OMS-Span ^ 80 solution were in Cast a stainless steel warring mixer. The mixer was then turned on for 3 minutes on high speed

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operated to create an emulsion. This emulsion was then poured into a preheated reaction vessel equipped with an Np flushing device, a stirrer, a thermometer and a. Was equipped with a reflux condenser. The heater was previously adjusted to the reaction temperature (generally 35 ° C) and thermostatically controlled to + 0.1 ⁰ G. The emulsion was then stirred for 1/2 hour while rinsing with Np before the initiator was added. The initiator was weighed to +0.0001 g in a tared weighing glass ("petticup") on a Mettler analytical balance, placed in a 10 ml beaker and dissolved in -5 ml acetone. This initiator / acetone solution was added to the stirring emulsion. The beaker was rinsed with an additional ~ 5 ml of acetone. The stopwatch was then started.

If an additive according to the invention was used to increase the reaction rate, it was generally incorporated before the initiator was added. In particular, it was added directly to the aqueous, inhibited acrylamide monomer, which was then stirred for 15 minutes ^{before emulsification with the OMS-Span ^ 3 80 solution.} The additives were weighed to the nearest 0.0001 g on a Mettler analytical balance. The solid additives, ie EA and NaEA, were weighed out on tared glassine weighing paper. The liquid chelating agent Versenex ^ 80 was weighed in tared weighing bottles. These ingredients were generally added undiluted to the aqueous, inhibited, 50 percent acrylamide solution. However, if these components were added to the emulsion, the solids were first pre-dissolved in a 10 ml beaker with a content of - ^ 5 ml triple distilled water.

The percentage conversion was determined by taking samples from the emulsion at certain times using a syringe of ^ 10 ml were taken. The syringes were each weighed together with the sample, then the polymer in acetone

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and the empty syringes were weighed back. The polymer was then filtered off on weighed filter paper. The percent conversion was determined gravimetrically after the polymer at 5O ⁰ C ~ to constant weight in a vacuum drying cabinet had been dried for 12 hours.

At constant polymer concentration and at constant temperature, the molecular weight of the polymer is direct proportional to the viscosity of the polymer solution. The ~ 12 Polymer, which had been dried for hours at 50 ° C. in a vacuum drying cabinet, was then processed using a micromill (model No. 502, Technilab Instruments) grind to a fine powder for about 3 minutes. 4.0 g of the polymer were with 24 ml Methanol, a nonsolvent, is mixed to make the polymer to wet before 198 ml of triple distilled water are quickly added to the mixture, which is stirred with a strong vortex became. If the solution became too viscous for the stirrer, a "tongue depresser" was used to stir the solution - ~ 5 minutes. A Brookfield viscometer, Model RVF with a No. 4 spindle and one speed of rotation of 4 rpm was used to measure the viscosity (in centipoise) of this 1.8 percent strength polymer solution used at 25 ° C.

Unless otherwise noted, this was the standard procedure used in all examples.

The original initiator concentration for all reactions listed in Table I was 0.1 g per 100 g of monomer (phm), correcting for the test conditions in each case. When EA was used, its concentration was 250 g per liter Million grams of monomer (ppm).

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557.075

- 13 Table I.

Initiator additive reaction time (h)

percentage Brookfield initial speed change viscosity of the poly (Cp) merization (% / h)

LUAzd®55 control 6th 95 12,000 46 EA 3 100 16,000 176 LUAZd®70 control 6th 82 17,000 35 EA 3 100 24 500 178 LUPERSOL® control 6th 88 20,000 41 223 EA 4th 100 18 5OC 172

Polymerization temperature: 35 C

Example 2

In this example Lupersol 256 was used as initiator at an initial concentration of 0.1 g per 100 g of monomer, correcting for the test conditions. The amount of erythorbic acid used was varied to determine how the reaction time and / or the molecular weight could be changed.

The results in Table II show that a certain amount of erythorbic acid is required in order to achieve a same or higher molecular weight of the polymer to achieve the increased reaction rate. Will this Amount exceeded, i.e. 250 to 500 ppm in this case, low molecular weight polymers can be improved with Establish polymerization rate.

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557.075 - 14 - conversion Brookfield Table II 95 Viscosity (cp) EA concentration Response time percentage 76 14 500 (ppm) (H) 89 - 0 (control) 6th 100 - 50 6th 100 20,000 100 6th 3,000 250 4th 500 2

Polymerization temperature: 35 C

Example 3

Monomeric acrylamide is sold commercially in solid form or as a 50 percent aqueous solution. The dissolved form contains about 25 ppm copper (II) sulfate, which acts as a polymerization inhibitor. Dow Chemical supplies the monomer in aqueous

Or)

ger shape and recommends the use of Versenex 80 for a more favorable rate of polymerization.

LupersoP-256 was reported for all in Table III Reactions used as initiator, the original concentration being 0.1 g per 100 g of monomer and corrected to the test conditions.

In this example, Versenex 80 was in the recommended concentration range compared with erythorbic acid in the usual concentration of 250 ppm. The results in Table II show that EA has a very beneficial reduction in overall reaction time to achieve 100 percent conversion allowed, whereby a high molecular weight polymer is formed.

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control - 6th 95 Versenex 80 2000 5 0 Versenex 80 500 6th 0 EA 250 4th 100

Table III

Additive Additive Con- Reaction Percentage Brookfield Initial Velocity Concentration time (h)! change in viscosity of the poly- (ppm) (Cp) merization (% / h)

14 500 47 0 0

20,000 174

Polymerization temperature 35 C

Example 4

The results in Table IV relate to reactions in which the initiator Lupersol 256 at a concentration of 0.1 g per 100 g of monomer was used, based on the test conditions has been corrected. If additives were used, these were used at a concentration of 250 g per 1 million g Monomer (ppm) used.

The preferred additives which gave nearly identical results are erythorbic acid and its alkali metal salts. In the case of vitamin B »there was a shorter conversion to 100 percent Reaction time required, but the result was a considerably reduced molecular weight of the polymer. In addition, the addition of vitamin Bp is very expensive.

Thus, both EA and NaEA cause a significant increase in the rate of polymerization and a decrease in the Response time until 100 percent conversion is achieved, w * obei compared to the control polymers of high molecular weight, as shown by the corresponding Brokkfield viscosity values.

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^ Y ₁ OYb Reaction
time (h) - 16 - 3432353 6th Tabel IV Additive 4th percentage
conversion Brookfield
viscosity
(Cp) Initial speed
the polymerization
(%/H) control 4th 95 14 500 47 EA 3 100 20,000 174 NaEA 100 21,000 174 Vitamin B" 100 2 500 ' 136

Polymerization temperature 35 C End of description

Claims (9)

Claims 1. Process for the production of a polymer or copolymer, characterized by inverse, aqueous emulsion polymerization of acrylamide in the presence of at least one surfactant, at least one free radical initiator, and about 50 to about 250 ppm of a component from the group erythorbic acid (isoascorbic acid), alkali metal salts of erythorbin * acid and mixtures thereof. 2. The method according to claim 1, characterized in that the alkali metal salt of erythorbic acid is sodium erythorbate used. 3- The method according to claim 1, characterized in that Munich - Bogcnhausen Phone: Telex: Fax (Il & HI -automat,):
mum im in ^ 7 Telegram: Chemindiis Munich the inverse, aqueous emulsion polymerization in one
Waoser-in-oil emulsion is carried out, the water being the disperse phase and the oil being the continuous phase. 4. The method according to claim 3, characterized in that the ratio of the water phase to the oil phase is about 1: 1 to is about 1: 5. 5. The method according to claim 1, characterized in that it is the surface-active agent or agents
is an oil-soluble agent with an HLB (hydrophile-lipophile balance) range of about 1 to 12. 6. The method according to claim 5, characterized in that the surface-active agent or agents in an amount
from about 0.5 to about 20.0 parts by weight per 100 parts by weight of the oil phase. 7. The method according to claim 1, characterized in that the polymerization temperature in the range of about 20 to about 8O ⁰ C. 8. The method according to claim 1, characterized in that the acrylamide concentration in the range of 30 to 60 parts by weight of the monomer per 100 parts by weight of water. 9. The method according to claim 1, characterized in that the initiator or initiators forming free radicals in the
Polymerization medium in the range of from about 0.005 to about 5.0 parts by weight per 100 parts by weight of the monomer
available.